gr013_polar2.py File Reference

Create and draw a polar graph with errors and polar axis in radians (PI fractions).

See the TGraphPolar documentation

Since TGraphPolar is a TGraphErrors, it is painted with TGraphPainter options.

With GetPolargram we retrieve the polar axis to format it see the TGraphPolargram documentation

 
import numpy as np
import ROOT
 
CPol = ROOT.TCanvas("CPol", "TGraphPolar Example", 500, 500)
 
theta = np.array([])
radius = np.array([])
etheta = np.array([])
eradius = np.array([])
 
for i in range(8):
    theta = np.append(theta, (i + 1) * (np.pi / 4.0))
    radius = np.append(radius, (i + 1) * 0.05)
    etheta = np.append(etheta, np.pi / 8.0)
    eradius = np.append(eradius, 0.05)
 
grP1 = ROOT.TGraphPolar(8, theta, radius, etheta, eradius)
grP1.SetTitle("")
 
grP1.SetMarkerStyle(20)
grP1.SetMarkerSize(2.0)
grP1.SetMarkerColor(4)
grP1.SetLineColor(2)
grP1.SetLineWidth(3)
# Draw with polymarker and errors
grP1.Draw("PE")
 
# To format the polar axis, we retrieve the TGraphPolargram.
# First update the canvas, otherwise GetPolargram returns 0
CPol.Update()
if grP1.GetPolargram():
    grP1.GetPolargram().SetToRadian()  # tell ROOT that the theta values are in radians

Author

Olivier Couet, Jamie Gooding

Definition in file gr013_polar2.py.